Electromagnetic device



Dec. 25, 1928. I

I I J. A. WOTTON ELECTROMAGNETIC mavrcs A, w 2 Mm m m m M 2 a M d m m Patented Dec. 25, 1928.

JAMES A. WOTTON, OF MONTCLAIR, NEW JERSEY,

COMPANY, INCORPORATED, OF NEW YORK, N. Y.,

ASSIGNOR TO WESTERN ELECTRIC A CORPORATION OF NEW YORK.

. ELECTROMAGNETIC DEVICE.

, Application filed May 22,

This invention relates to electromagnetic devices and particularly to electromagnetic relays for use in party line telephone systems.

Heretofore relays of this character have been particularly subject to damage through high voltage discharges caused by lightning induction. Such relays necessarily were designed to be slow acting so as to respond steadily to ringing currents, features of such design being a large heavy armature and a U shaped iron frame to the middle portion of which the core was attached. Since therefore the outer turns of the winding were placed near to and parallel with such frame and since the frame was grounded there was formed a small air gap between such outer turns and ground across which lightning induction discharges invariably jumped with consequent serious damage to the winding.

An object of the invention is to make certain improvements in the construction of such relays whereby damage by high voltage discharges ma be prevented.

A feature 0 the invention is a connection constituting a path of low impedance between the winding and the frame whereby the air gap path between these points is short cir-- cuited.

Another feature of the invention is a new arrangement of contact springs whereby a ground connection is removed from the frame of the relay and whereb an air gap is formed between the frame an one of such contact springs rather than between the frame and the winding.

Other features of this invention will be apparent from the followin description and detailed drawing wherein igs. 1 and 2 are side and front views respectively showing the arts of the relay embodying the invention. Fig. 3illustrates a four-party selective ringing system in which the relay embodying the invention is to be used. However, it will be understood that these relays may also be employed in other party selective ringing systems other: than the one herein described.

As shown in the drawing the electromagnetic relay comprises a core 10 with a winding 11 therefor which is held in a rigid manner to the U-shaped frame or pole piece 12 and the mounting plate 13 on which the device is mounted by means of a screw 30 which 1924. serial No. 714,996.

extends upward through the mounting plate, fralne and into the core 10 of the magnet.

The heads of the magnet spool are formed of square and round insulating blocks 14 and 15 respectively, which fit closely within the space provided by the two extensions of the frame 12. The upper extremities of the frame are secured to the opposite sides of the block 14 by screws 16. This block or head 14 carries two posts 17 and 17' which are covered with felt and which are located in predetermined positions for forming limiting stops for the movement of the inverted u shaped armature 18 which is pivoted to the lower part of the frame by screws 19. The insulating block 14 also carries a terminal 20 to which is connected one end of the magnet winding. The other end of the winding 20 is connected to the terminal member 21 which is fastened to the frame 12 by the screws 22. Held by means of screws 24, between plate 31 and the arm 23 of the member 21. and insulatedfrom each other and the frame are flexible contact springs 25 and 26 (which are in direct contact with the terminals 32 and 33 respectively) the movements of which are controlled by the spring member 27 which is carried by and fastened to the armature 18 by the pivot screws 19 and screw 28. An insulating member 29 is provided for engaging the contact spring 25 to close the contacts 34 when the relay is 0perated.

Referring to Fig. 3, which shows a well known four-party selective ringing system wherein relays, according to this invention, are employed. the terminal 20 of the relay at each station is connected through the lefthand windin of the induction coil 36 to the tip side M of the line and terminal member 20' is connected through the condenser 35 to the ring side L of the line. At each of the four stations shown, one of the terminals 32 or 33 is connected to ground either direct or through the bell. In case a high voltage inductive charge is'im ressed on the line it will find a discharge pat between the frames of the relays and the grounded contact springs, across which it can jum without arcing between the winding and t e frame What is claimed is': I

1. In an electromagnetic device, a winding, a metallic frame surrounding this windion ing, one end or said winding being connected to said frame, and a terminal mounted in close proximity to said frame so as to form an air gap between said terminal and said frame of a predetermined value such that the impedance of said air gap is less than the impedance of said winding.

2. In an electromagnetic device, a winding, terminals connected with the opposite ends of said winding, a metallic frame surrounding said winding, a grounded contact member mounted upon and a short distance from said frame but insulated therefrom, and a connection between one of said terminals and said frame whereby high potential surges flowing into said winding will be shunted from the winding over the gap between said frame and said contact member to ground.

3. In an electromagnetic device a winding, a metallic frame surrounding said winding, one end of said winding being connected to said frame, and a terminal'mounted in close proximity to said frame so as to form an air gap between said terminal and said frame of a predetermined value such that the impedanceof said air gap is less than the impedance of any other path between said winding and the said frame.

In witness whereof, I hereunto subscribe my name this 21 day of May A. 1)., 1924.

, JAMES A. WVOTTON. 

